Yeah, Here is a quick focus test to separate calibration from optical issues. Set a book on a table at a slight angle, choose single point AF, and focus on a specific line of text near the middle at the widest aperture. Take several shots and review at high magnification to see where the sharpest plane landed. If it consistently sits in front or behind that line, use AF fine tune on the body to correct. Do the same scene using live view with magnified manual focus. If those frames are tack sharp, the optics are probably fine and it is a focus calibration problem. If nothing looks truly crisp even around f8 at different distances and that suggests an internal issue that needs a technician. Quick sanity check as well adjust the diopter so the viewfinder display looks perfectly sharp. Short but important.
